Call round for old and new pal (5)
I believe the answer is:
crony
'pal' is the definition.
(synonyms)
'call round for old and new' is the wordplay.
'call' becomes 'cry' (as in a bird's call).
'round' indicates putting letters inside.
'for old' becomes 'o' (I can't justify this - if you can you should believe this answer much more).
'and' is a charade indicator (letters next to each other).
'new' becomes 'n' (abbreviation as in New Testament NT).
'o'+'n'='on'
'cry' placed around 'on' is 'CRONY'.
Can you help me to learn more?
(Other definitions for crony that I've seen before include "Corny (anag.)" , "Close companion" , "Sidekick" , "Close friend" , "mate" .)